FDA approves Gilead’s once-daily HIV combination Stribild

Gilead has won US approval for its four-in-one tablet Stribild after the drug was approved by the Food and Drug Administration (FDA) as part of a once-daily regimen.

Combining HIV medicines elvitegravir, cobicistat, emtricitabine and tenofovir disoproxil fumarate into one pill, Stribild (previously known as Quad) offers a less complicated option for people with HIV-1 who have yet to undergo treatment.

“Through continued research and drug development, treatment for those infected with HIV has evolved from multi-pill regimens to single-pill regimens,” said Dr Edward Cox, director of the Office of Antimicrobial Products in FDA's Center for Drug Evaluation and Research. “New combination HIV drugs like Stribild help simplify treatment regimens.”

The approval is based on data from two phase III studies that demonstrated non-inferiority compared to Gilead's other once-daily combination pill Atripla, as well as to a regimen containing ritonavir-boosted atazanavir plus Truvada in suppressing the viral load.

Gilead recorded $3.2bn in Atripla sales during 2011, although the company had to share total revenues with Bristol-Myers Squibb, which holds rights to one of the drugs involved in the combination, making it likely Gilead will push marketing efforts towards its newer drug Stribild, for which Gilead holds complete rights.

The company also has another combination HIV product, Complera, although the licence to one of the ingredients is held by Janssen, again potentially making Stribild the more attractive option for Gilead.

Of Stribild's ingredients, emtricitabine and tenofovir disoproxil fumarate have already been approved by the FDA as a combination pill called Truvada, while elvitegravir and cobicistat have both yet to receive individual approval.

Each ingredient works in a different way to treat the virus, with elvitegravir interfering with one of the enzymes that HIV needs to multiply and cobicistat inhibiting an enzyme that metabolises certain HIV drugs so the effect of elvitegravir is prolonged.

The combination of emtricitabine and tenofovir disoproxil fumarate blocks the action of another enzyme that HIV needs to replicate in a person's body.

“Together, these drugs provide a complete treatment regimen for HIV infection,” said the FDA.

The approval does come with a boxed warning, however, alerting patients and healthcare professionals that the drug can cause a build up of lactic acid in the blood and severe liver problems, both of which can be fatal. In addition, the warning states that Stribild is not approved to treat chronic hepatitis B virus infection.

Other side effects reported in trials included decreased bone mineral density, fat redistribution and changes in the immune system.

As part of its approval conditions, Gilead will have to conduct additional studies to determine the drug's safety in women and children, as well as further investigate how resistance develops to Stribild and the possibility of interactions between Stribild and other drugs.

Applications for marketing approval of Stribild are also pending in Australia, Canada and the European Union, while Gilead has granted several companies in India and the Medicines Patent Pool the right to develop generic versions of Stribild and distribute them to 100 developing countries.